Selection of refractory and permissive strains of Aedes triseriatus (Diptera : Culicidae) for transovarial transmission of La Crosse virus

The genetic basis of transovarial transmission of La Crosse virus in Aedes triseriatus (Say) was investigated through selection experiments on 2 mosqu ito strains. One strain was subject to selection for transovarial transmiss ion refractoriness, the other for permissiveness to transovarial transmissi on. Response to selection for a low filial infection I ate was rapid, decre asing from 18 to 3% in 3 generations. However, no response to selection for permissiveness was observed in the other strain; the average filial infect ion rates through 4 generations fluctuated between 25 and 40%. By contrast, the transovarial transmission rate in both strains showed a consistent res ponse to selection in both directions. These patterns are consistent with a model in which transovarial transmission is controlled by a single genetic locus and permissiveness is conditioned by dominant alleles; whereas the f ilial infection rate is nongenetic and influenced by stochastic factors in the mosquito and virus.